[rom-e2e] define, splice and test keymgr_rom_ext_meas_en
[rom-e2e] define, splice and test keymgr_rom_ext_meas_en

Add tests to use a true OWNER_SW_CFG_ROM_KEYMGR_ROM_EXT_MEAS_EN spliced
into the OTP. Original test is preserved, this adds:
//sw/device/silicon_creator/rom/e2e:rom_e2e_keymgr_init_rom_ext_meas
functests.

Fixes:#14501
Signed-off-by: Drew Macrae <32d48ac45113625c0a04afe7343eae478a303684@google.com>

lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan